The need for energy efficiency is often at odds with established patterns of human behaviour. It is often difficult to balance convenience with a reduction in energy use in a home or office where other matters may take priority, such as dealing with work projects or family needs. In many cases lights or other electrical devices are left on in a space, thereby expending energy without the presence of people in the space.
Prior art solutions dealing with this problem include the use of motion sensors and counters that are hard-wired to local light switches to turn off the lights when people are not present. However, these solutions have a number of short-comings. First, because the motion sensors or counters have to be hard-wired to the light switch, the cost and hassle of installing such devices in a building becomes significant, especially in buildings with many rooms and spaces.
Second, room counters are configured to count the number of entries and exits to a space (e.g. as disclosed in U.S. Pat. No. 5,374,854). If a parent carries a child into an empty room, the counter will only count one entry to the room. And if the parent or child leaves separately, the count will be decremented and the lights will go out despite the fact that someone is left within the room. Moreover, because a counter is designed to be hard-wired to the light switch two additional problems arise. First, if the room has multiple doorways there is no way to reconcile information collected by counters provided at each doorway to the room. As such, a counter can only be used effectively if the room has only one doorway. Second, the space must be enclosed, which means spaces around a building cannot employ counters. The counters described in the prior art cannot be used to control the lights in a space outside of the building, such as in a garden or landing area.